It is well known that exposure to the sun's ultraviolet radiation can cause a myriad of health problems, ranging from simple sunburns to severely malignant forms of cancer, such as melanoma. It is also well known that the application of a sunscreen composition to the skin can significantly reduce the effects of the sun's UV radiation.
Sunscreen compositions have been in use for decades and have been formulated to block the sun's UV photons. Organic chemical molecules such as para-aminobenzoic acid (PABA) contain conjugated pi systems and are therefore able to absorb UV photons, effectively blocking the UV radiation. Inorganic particulates such as zinc oxide block UV radiation by reflecting or scattering the UV photons. However, the size of the inorganic particulate must be matched to the wavelength of the UV radiation for proper effect. In addition to organic chemical molecules and inorganic particulates, a newer class of molecules, organic particulates such as Tinosorb M, are being used in sunscreen compositions. Organic particulates block UV radiation by absorbing and reflecting the UV photons. Like the inorganic particulates, the size of the organic particulate must be matched to the wavelength of the UV radiation for proper effect.
A particular sunscreens ability to block the sun's UV radiation can be quantified by the sun protection factor (SPF), an integer number typically ranging from about 2 to about 100. The higher the SPF integer, the greater the ability to block UV radiation, although the claimed increase in effectiveness of compounds having SPF numbers higher than about 50 is being questioned. The SPF is dependent on both the composition of the sunscreen and the amount applied to a given area. The SPF of a specific sunscreen is based on the uniform application of about 2 mg of sunscreen to a square centimeter of exposed skin (i.e., about 2 mg/cm2). The exposed surface area of an average adult human's back is approximately 3,114 cm2 and the exposed surface area of an adult human's entire body is approximately 16,300 cm2, requiring about 6.2 grams and about 32.6 grams of sunscreen to meet the SPF requirements, respectively. See Table 1, adapted from A simple measure for applying sunscreen while on holidays, Dermatology Journal Online, Vol. 3, No. 9; this reference is incorporated herein by reference in its entirety.
TABLE 1Exposed Surface Area of Average Adult Human BodySurfaceRecommendedSegmentPercentage(cm2)Dosage (mg)Face, neck<9%6851,370Upper limb (right) 9%1,5573,114Upper limb (left) 9%1,5573,114Back18%3,1146,228Torso18%3,1146,228Lower limb (right)18%3,1146,228Lower limb (left)18%3,1146,228
Typically, sunscreen is formulated as a gel or lotion, although aerosol sprays have lately been added to the market. Regardless of the formulation, an even distribution of the sunscreen on the user's skin is required for effective protection from the sun's UV radiation. Gel and lotion formulations are often viscous and difficult to apply evenly over the skin, resulting in areas saturated with sunscreen and other areas which are under-treated and prone to UV damage. Certainly the presence of body hair commonly found on the chests, backs and legs of adult makes the even application of viscous gel and lotion formulations less likely. In an attempt to help aid the thorough and even application of sunscreen, aerosol sprays were developed. Instead of rubbing viscous lotions over their skin, users were able to simply spray the sunscreen on their exposed skin. However, environmental factors such as rain or wind can affect the distribution. In addition, aerosol sprays can be difficult to use to reach all areas of the human body, such as the back, and users are sometimes hesitant to use aerosol sprays around sensitive areas such as the eyes and mouth. In addition, liquids, aerosol sprays, gels and lotions are typically not allowed aboard an aircraft due to security restrictions and regulations.
Another drawback of gels, lotions, aerosol sprays and even towelettes impregnated with sunscreen compositions is that the user is not able to adequately apply a thorough and even coating to their body, especially their back, without the assistance of someone else.
In addition to this size constraint, the towelettes are usually fragile when impregnated with sunscreen, so tearing can easily occur. Finally, the towelettes are a one-time use product and are to be discarded after only one application of sunscreen, usually to the human face.